Asymptotic effectiveness – NTU formulas for multipass plate heat exchangers

Abstract

The effectiveness of a plate heat exchanger with finite number of plates is affected by the end channels, and the channels between two adjacent passes. these effects become less significant as the number of plates becomes large, N>40, as shown by Kandlikar and Shah (1987). in the present paper, plate heat exchangers are represented by assemblies of individual parallel/counterflow heat exchangers having infinite numbers of plates. Closed-form equations for these assemblies are derived in terms of thermal effectiveness P1 as a function of the capacity rate ration R1 and the number of transfer units NTU1 for the following pass arrangements: 1-1, 2-1, 2-2, 3-1, 3-2, 3-3, 4-1, 4-2 and 4-4.